<template>
    <ul class="list">
        <li  @click="handleLetterClick" class="item" v-for="item of letters" :key="item"
         @touchstart='handleTouchStart'
         @touchmove ='handleTouchMove'
         @touchend ='handleTouchEnd'
         :ref="item"
         >{{item}}</li>
    </ul>
</template>
<script>
export default {
    name:'CityAlphabet',
    props:{
        cities:Object
    },
    data(){
        return {
            touchStatus:false,
            startY:0,
            timer:null
        }
    },
    computed:{
        letters(){
            const letters =[]
            for (let i in this.cities){
                letters.push(i)
            }
            return letters
        }
    },
    updated (){
        this.startY = this.$refs['A'][0].offsetTop
    },
    methods:{
        handleLetterClick(e){
            // console.log(e.target.innerText)
            this.$emit('change',e.target.innerText)
        },
        handleTouchStart(){
            this.touchStatus=true
        },
        handleTouchMove(e){
            if(this.touchStatus){
                if(this.timer){
                    clearTimeout(this.timer)
                }
                this.timer= setTimeout(()=>{
                    // const statusY=this.$refs['A'][0].offsetTop
                    const touchY = e.touches[0].clientY-79
                    const index=Math.floor((touchY-this.startY)/20)
                    // console.log(statusY)
                    // console.log(touchY)
                    // console.log(index)
                    if(index>=0 && index<this.letters.length){
                        this.$emit('change',this.letters[index])
                    }
                 },16)
            }
        },
        handleTouchEnd(){
            this.touchStatus=false
        }
    }
}
</script>
<style lang="stylus" scoped>
@import '~@/assets/styles/varibles'
.list
    display:flex
    flex-direction :column
    justify-content:center
    position:absolute
    top:1.58rem
    right:0
    bottom:0
    width:.4rem
    .item
        line-height:.4rem    
        text-align :center
        color:$bgColor

</style>
